Macrotocinclus flexilis (peppered Oto)

Macrotocinclus flexilis which is also known as the peppered Oto belongs to the Hypoptopomatinae subfamily, Loricariidae family and Siluriformes order. The species may also be known as Ototinclus flexilis, Otocinclus fimbriatus, and Otocinclus arnoldi. The species was reclassified from otocinclus to macrotocinclus by Isbrucker and Seidel.
The species is native to South America (Argentina, Paraguay,
Uraguay, Brazil). The peppered Oto occurs in clear waters and rarely in black waters. In general, Macrotocinclus species as its former genus (Otocinclus), occur in well-oxygenated headwaters of main rivers of South America with vegetation and moderate to slow flowing movement. The water has a high amount of tannin due to the decomposition of leaves and wood that makes the water tea-colored (an indication of soft and acidic habitat). Furthermore, the species occur in seasonally flooded rainforests.
Macrotocinclus flexilis has an elongated body covered with plates except for its abdomen. As with almost all catfishes, the peppered Oto has a smooth and flat belly. Macrotocynclus have a pair of barbels around the mouth that are used as tactile organs to obtain physical information about objects, to find food and in courtship. There are two color forms of the species, a dark olive-brown to green coloration similar to corydoras’ paleatus coloration and a darker pigmented body. Because of the similarity among the macrotocinclus and otocinclus species get confused as other species by aquarists as well as by scientists. For example, in the aquarium trade, different otocinclus species are sold as otocinclus affinnis. The species get up to 2.1 inches length (5.4 cm) with females being broader in breeding conditions and slightly larger than males. The species have a lifespan of 5 years.
The species has a peaceful temperament that makes it ideal in community tanks with other nonviolent small size species. It’s advised to keep the species at least in a group of 6 individuals and more due to their schooling behavior. Because of the natural habitat of the peppered Oto should be kept in soft acidic water. The species is not a good option for a beginner because Macrotocinclus species require clean water with stable parameters. A pH between 6.5-7.5, with a temperature between 18-24 Celsius, and a hardness between 2-25 dGH, suits the species.
The species need a reasonable space because macrotocinclus is a schooling fish and requires high oxygenated waters with stable water parameters. The water parameters are easier to maintain in balance in bigger tanks. An aquarium with 60 liters of water (15,85 gallons) is suitable for a shoal of 6 peppered Otos. Plants provide shelter for stressed fish as well as producing chemical and physical conditions for the growth of microorganisms that can be eaten by the Otocinclus.
Macrotocinclus flexilis are excellent algae eaters. They continually clean the algae from the glass and the decoration but like all animals need a proper diet. They eat prepared food (sinking pellets), fresh steamed vegetables (lettuce, spinach) and small live-foods such as bloodworms.
In general, there are few occurrences of breeding reports of Macrotocinclus and Otocinclus species in captivity. The species have a similar breeding habit with corydoras species.

Otocinclus arnoldi (1) by CHUCAO/ is liscenced under
CC BY-SA 3.0


  1. Hans-Georg Evers and Ingo Seidel 2005, Catfish Atlas Vol. 1, published by Hans A. Baensch, ISBN 388240643
  2. Otocinclus flexilis TSN 164355. Retrieved from
  3. Marcelo R. Britto and Cristiano, R. Moreira 2002, Otocinclus tapirape: A New Hypoptopomatine Catfish from Central Brazil Siluriformes Loricariidae. Retrieved from
  4. Richard Geis 1999, Catfish, TFH publications, ISBN 0791050890
  5. Otocinclus flexilis. Retrieved from
  6. Otocinclus flexilis. Retrieved from

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